Techniques (pattern-forming techniques) in which a fine pattern is formed on top of a substrate, and a lower layer beneath that pattern is then processed by conducting etching with the pattern as a mask are widely used in the semiconductor industry for IC fabrication and the like, and are attracting considerable attention.
These fine patterns are typically formed from an organic material, and are formed, for example, using a lithography method or a nanoimprint method or the like. For example, in the case of a lithography method, a process is conducted in which a resist film formed from a resist composition containing a base component such as a resin is formed on top of a support such as a substrate, the resist film is subjected to selective exposure using radiation such as light or an electron beam, through a mask in which a predetermined pattern has been formed (a mask pattern), and a developing treatment is then conducted, thereby forming a resist pattern of predetermined shape in the resist film. Resist compositions in which the exposed portions change to become soluble in the developing solution are termed positive compositions, whereas resist compositions in which the exposed portions change to become insoluble in the developing solution are termed negative compositions.
Then, using this resist pattern as a mask, a semiconductor device or the like is produced by conducting a step in which the substrate is processed by etching.
In recent years, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization. Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays semiconductor device mass production using KrF excimer lasers and ArF excimer lasers has already commenced, and for example, lithography using ArF excimer lasers has enabled pattern formation with resolution at the 45 nm level. Furthermore, in order to further improve the resolution, research is also being conducted into lithography techniques that use exposure light sources having a wavelength shorter than these excimer lasers, such as F2 excimer lasers, electron beams, EUV (extreme ultra violet radiation), and X rays.
The resist composition requires lithography properties such as a high level of sensitivity to these types of exposure sources, and a high resolution capable of reproducing patterns of minute dimensions. An example of a resist material that satisfies these requirements is a chemically amplified resist composition, which includes a base component that exhibits changed alkali solubility under the action of acid and an acid generator that generates acid upon exposure (for example, see Patent Document 1). For example, a positive chemically amplified resist typically contains, as a base component, a resin that exhibits increased alkali solubility under the action of acid, and during formation of a resist pattern, when acid is generated from the acid generator by exposure, the exposed portions of the resist become alkali-soluble.
Recently, a new lithography technique called the double patterning method has been proposed, in which a pattern is formed by conducting patterning two or more times (see, for example, Non-Patent Documents 1 and 2). It is considered that by using this double patterning method, a pattern can be formed that is finer than a pattern formed using only a single patterning step.
[Patent Document 1]
Japanese Unexamined Patent Application, First Publication No. 2003-241385
[Non-Patent Document 1]
Proceedings of SPIE, vol. 5256, pp. 985 to 994 (2003)
[Non-Patent Document 2]
Proceedings of SPIE, vol. 6153, pp. 1 to 7 (2006)